First example of a borate-bridged dimeric aluminum Schiff-base complex containing five-coordinate metal centers

Abstract

The formation of a borate-bridged dimeric aluminum Schiff-base compound [salen(^tBu)Al]₂O₂BOMe [salen = N,N′-ethylenebis(salicylidenimine) (1) has been reported. Complex 1 crystallizes in a triclinic P₁ space group with a = 14.57, b = 15.15, c = 15.84 Å and α = 96.92, β = 90.82, γ = 105.53°. The crystal structure shows the presence of a metaborate (MeOBO₂²⁻) bridge between two five-coordinate aluminum atoms with a bridging OBO angle of 123.25°. The compound has been characterized by ¹H, ¹³C, ¹¹B, ²⁷Al NMR, IR and mass spectroscopies and melting point measurements. ¹H NMR shows two complex multiplets for the ^tBu groups and two different environments for the imine protons. ¹¹B NMR shows a peak at 18 ppm characteristic of three-coordinate boron and ²⁷Al NMR shows a peak at 29 ppm characteristic of five-coordinate aluminum.